My bungalow and garage both have what is known as a wet-laid slate
roof (small slates bedded onto mortar), built in 1960. Ferns have
established themselves on the north side of both roofs, where it's
shaded. The roots have worked their way under the mortar layer. I
don't know what species of fern they are. They survived this year's
heat wave and drought. They don't seem to be doing any harm, but I'd
rather they weren't there. A couple of years ago I tried spraying them
with glyphosate, but with little effect. Are ferns impervious to
glyphosate? Should I use something else, if so, what? Any other
suggestions.

--
Chris

Gardening in West Cornwall, very mild, sheltered
from the West, but open to the North and East.

In article <rkumnhtkdgoo3phn75td3vfaueddqd17p9@4ax.com>,
me@privacy.net says...
>
> My bungalow and garage both have what is known as a wet-laid slate
> roof (small slates bedded onto mortar), built in 1960. Ferns have
> established themselves on the north side of both roofs, where it's
> shaded. The roots have worked their way under the mortar layer. I
> don't know what species of fern they are.

Many ferns can grow an expanding root that would do
your slates no good at all.

They survived this year's
> heat wave and drought. They don't seem to be doing any harm, but I'd
> rather they weren't there. A couple of years ago I tried spraying them
> with glyphosate, but with little effect. Are ferns impervious to
> glyphosate? Should I use something else, if so, what? Any other
> suggestions.

Farm suppliers can be helpful

iirc Tony McCormac laid a strip of copper along his roof
ridge to poison moss and avoid roof troubles.

Janet

On 21/11/2022 13:56, Janet wrote:
> In article <rkumnhtkdgoo3phn75td3vfaueddqd17p9@4ax.com>,
> me@privacy.net says...
>>
>> My bungalow and garage both have what is known as a wet-laid slate
>> roof (small slates bedded onto mortar), built in 1960. Ferns have
>> established themselves on the north side of both roofs, where it's
>> shaded. The roots have worked their way under the mortar layer. I
>> don't know what species of fern they are.
>
> Many ferns can grow an expanding root that would do
> your slates no good at all.
>
>
> They survived this year's
>> heat wave and drought. They don't seem to be doing any harm, but I'd
>> rather they weren't there. A couple of years ago I tried spraying them
>> with glyphosate, but with little effect. Are ferns impervious to
>> glyphosate? Should I use something else, if so, what? Any other
>> suggestions.
>
> Farm suppliers can be helpful
>
> iirc Tony McCormac laid a strip of copper along his roof
> ridge to poison moss and avoid roof troubles.
>
> Janet

BAC50 (50% Benzalkonium Chloride) will kill moss / plants etc. and often
is what the professionals use in roof and path cleaning. Dilute and use
a garden sprayer on a winless dry day. Wear mask and eye protection.

It's not instant but over 3 months you should see a much improved roof
and it will continue to work for much longer. The weather will start
washing off the dead matter.

Example showing warning label
https://www.ebay.co.uk/itm/154842620292
https://www.ebay.co.uk/itm/154842620292

--
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